Reviewed by Jared Jensen
Secondary Review NO TITLE, 2012 10
This proposal aims to understand the effectors required for Xanthomonas oryzae pv oryzicola, a
bacterial pathogen of rice, to elicit a nonhost HR-like response in barley. The maize gene Rox1
has been found to be an NB-LRR R gene to X. oryzae pv oryzicola, specifically to the conjugate
gene named AvrRozx1. When Rox1 is expressed in other plant systems, they to gain resistance
to AvrRox1 containing X. oryzae oryzicola strains. With this knowledge this study wants to look
deeper into potential effectors that the pathogen might have enabling it to elicit an HR-like
response in a nonhost. The author hypothesizes that X. oryzae pv oryzicola is thought to have
an effector that elicits plant defenses and prevents colonization and disease in nonhosts.
This project is divides into two main objectives. 1) Determine the molecular trigger(s) of an Hrlike response to ZX. oryzae pv oryzicola by barley. And 2) compare transcriptional response of
barley to infection with host and nonhost Xanthomonas pathogens to identify candidate host
genes that regulate nonhost defense response. By understanding host genes that recognize the
pathogen in barley (r genes), the author hopes to take this understanding and transform those
genes into rice for novel resistance mechanisms.
The first objective’s approach centers on the transformation of candidate xanthomonas oyrzae
pv oyrzicola effectors into Xanthomonas campestris (a non pathogen of barley, expressing no
response) then screened for a phenotypic HR-like response. The second objective aims to look
at transcriptional differences of barley in response to infection with pathogens and nonpathogens as well as a mock control. Any genes identified that are up regulated or down
regulated will be confirmed with VOX and VIGS, respectively.
Overall this proposal has a good understanding of the current problems, and potential ways to
help solve them. Here they are planning to look for effectors that contribute to non-host HRlike responses, and then genes that are differentially expressed in the presence of a nonpathogen. The experimental design for both objectives seems feasible with specific obtainable
goals. One potential problem not addressed for objective 2 would be any contingency plans
should they not find any genes that are significantly up/down regulated upon pathogen
infection. The author successfully details obtainable results and how these results could be
used in the future. Specifically, looking for R-genes corresponding to HR-eliciting effectors
found in this study.
Score: Excellent
I give this proposal an excellent rating due to its probability of completion, thoughtful
experimental design, and future directions it wants to take these results.